[Archive] Don't throw away errors for malformed archive members

When adding an archive member with a problem, e.g. a new bitcode with an
old archiver, containing an unsupported attribute, or an ELF file with a
malformed symbol table, the archiver would throw away the error and
simply add the member to the archive without any symbol entries. This
meant that the resultant archive could be silently unusable when not
using --whole-archive, and result in unexpected undefined symbols.

This change fixes this issue by addressing two FIXMEs and only throwing
away not-an-object errors. However, this meant that some LLD tests which
didn't need symbol tables and were using invalid members deliberately to
test the linker's malformed input handling no longer worked, so this
patch also stops the archiver from looking for symbols in an object if
it doesn't require a symbol table, and updates the tests accordingly.

Differential Revision: https://reviews.llvm.org/D88288

Reviewed by: grimar, rupprecht, MaskRay

include/llvm/Object/SymbolicFile.h

@@ -173,6 +173,8 @@ public:
   static bool classof(const Binary *v) {
     return v->isSymbolic();
   }
+
+  static bool isSymbolicFile(file_magic Type, const LLVMContext *Context);
 };
 
 inline BasicSymbolRef::BasicSymbolRef(DataRefImpl SymbolP,

lib/Object/ArchiveWriter.cpp

@@ -359,22 +359,21 @@ getSymbols(MemoryBufferRef Buf, raw_ostream &SymNames, bool &HasObject) {
   // reference to it, thus SymbolicFile should be destroyed first.
   LLVMContext Context;
   std::unique_ptr<object::SymbolicFile> Obj;
-  if (identify_magic(Buf.getBuffer()) == file_magic::bitcode) {
+
+  const file_magic Type = identify_magic(Buf.getBuffer());
+  // Treat unsupported file types as having no symbols.
+  if (!object::SymbolicFile::isSymbolicFile(Type, &Context))
+    return Ret;
+  if (Type == file_magic::bitcode) {
     auto ObjOrErr = object::SymbolicFile::createSymbolicFile(
         Buf, file_magic::bitcode, &Context);
-    if (!ObjOrErr) {
-      // FIXME: check only for "not an object file" errors.
-      consumeError(ObjOrErr.takeError());
-      return Ret;
-    }
+    if (!ObjOrErr)
+      return ObjOrErr.takeError();
     Obj = std::move(*ObjOrErr);
   } else {
     auto ObjOrErr = object::SymbolicFile::createSymbolicFile(Buf);
-    if (!ObjOrErr) {
-      // FIXME: check only for "not an object file" errors.
-      consumeError(ObjOrErr.takeError());
-      return Ret;
-    }
+    if (!ObjOrErr)
+      return ObjOrErr.takeError();
     Obj = std::move(*ObjOrErr);
   }
 
@@ -393,7 +392,7 @@ getSymbols(MemoryBufferRef Buf, raw_ostream &SymNames, bool &HasObject) {
 static Expected<std::vector<MemberData>>
 computeMemberData(raw_ostream &StringTable, raw_ostream &SymNames,
                   object::Archive::Kind Kind, bool Thin, bool Deterministic,
-                  ArrayRef<NewArchiveMember> NewMembers) {
+                  bool NeedSymbols, ArrayRef<NewArchiveMember> NewMembers) {
   static char PaddingData[8] = {'\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n'};
 
   // This ignores the symbol table, but we only need the value mod 8 and the
@@ -494,13 +493,17 @@ computeMemberData(raw_ostream &StringTable, raw_ostream &SymNames,
                       ModTime, Size);
     Out.flush();
 
-    Expected<std::vector<unsigned>> Symbols =
-        getSymbols(Buf, SymNames, HasObject);
-    if (auto E = Symbols.takeError())
-      return std::move(E);
+    std::vector<unsigned> Symbols;
+    if (NeedSymbols) {
+      Expected<std::vector<unsigned>> SymbolsOrErr =
+          getSymbols(Buf, SymNames, HasObject);
+      if (auto E = SymbolsOrErr.takeError())
+        return std::move(E);
+      Symbols = std::move(*SymbolsOrErr);
+    }
 
     Pos += Header.size() + Data.size() + Padding.size();
-    Ret.push_back({std::move(*Symbols), std::move(Header), Data, Padding});
+    Ret.push_back({std::move(Symbols), std::move(Header), Data, Padding});
   }
   // If there are no symbols, emit an empty symbol table, to satisfy Solaris
   // tools, older versions of which expect a symbol table in a non-empty
@@ -564,8 +567,9 @@ static Error writeArchiveToStream(raw_ostream &Out,
   SmallString<0> StringTableBuf;
   raw_svector_ostream StringTable(StringTableBuf);
 
-  Expected<std::vector<MemberData>> DataOrErr = computeMemberData(
-      StringTable, SymNames, Kind, Thin, Deterministic, NewMembers);
+  Expected<std::vector<MemberData>> DataOrErr =
+      computeMemberData(StringTable, SymNames, Kind, Thin, Deterministic,
+                        WriteSymtab, NewMembers);
   if (Error E = DataOrErr.takeError())
     return E;
   std::vector<MemberData> &Data = *DataOrErr;

lib/Object/SymbolicFile.cpp

@@ -41,20 +41,14 @@ SymbolicFile::createSymbolicFile(MemoryBufferRef Object, file_magic Type,
   if (Type == file_magic::unknown)
     Type = identify_magic(Data);
 
+  if (!isSymbolicFile(Type, Context))
+    return errorCodeToError(object_error::invalid_file_type);
+
   switch (Type) {
   case file_magic::bitcode:
-    if (Context)
-      return IRObjectFile::create(Object, *Context);
-    LLVM_FALLTHROUGH;
-  case file_magic::unknown:
-  case file_magic::archive:
-  case file_magic::coff_cl_gl_object:
-  case file_magic::macho_universal_binary:
-  case file_magic::windows_resource:
-  case file_magic::pdb:
-  case file_magic::minidump:
-  case file_magic::tapi_file:
-    return errorCodeToError(object_error::invalid_file_type);
+    // Context is guaranteed to be non-null here, because bitcode magic only
+    // indicates a symbolic file when Context is non-null.
+    return IRObjectFile::create(Object, *Context);
   case file_magic::elf:
   case file_magic::elf_executable:
   case file_magic::elf_shared_object:
@@ -95,6 +89,39 @@ SymbolicFile::createSymbolicFile(MemoryBufferRef Object, file_magic Type,
         MemoryBufferRef(BCData->getBuffer(), Object.getBufferIdentifier()),
         *Context);
   }
+  default:
+    llvm_unreachable("Unexpected Binary File Type");
+  }
+}
+
+bool SymbolicFile::isSymbolicFile(file_magic Type, const LLVMContext *Context) {
+  switch (Type) {
+  case file_magic::bitcode:
+    return Context != nullptr;
+  case file_magic::elf:
+  case file_magic::elf_executable:
+  case file_magic::elf_shared_object:
+  case file_magic::elf_core:
+  case file_magic::macho_executable:
+  case file_magic::macho_fixed_virtual_memory_shared_lib:
+  case file_magic::macho_core:
+  case file_magic::macho_preload_executable:
+  case file_magic::macho_dynamically_linked_shared_lib:
+  case file_magic::macho_dynamic_linker:
+  case file_magic::macho_bundle:
+  case file_magic::macho_dynamically_linked_shared_lib_stub:
+  case file_magic::macho_dsym_companion:
+  case file_magic::macho_kext_bundle:
+  case file_magic::pecoff_executable:
+  case file_magic::xcoff_object_32:
+  case file_magic::xcoff_object_64:
+  case file_magic::wasm_object:
+  case file_magic::coff_import_library:
+  case file_magic::elf_relocatable:
+  case file_magic::macho_object:
+  case file_magic::coff_object:
+    return true;
+  default:
+    return false;
   }
-  llvm_unreachable("Unexpected Binary File Type");
 }

test/Object/archive-malformed-object.test

@@ -0,0 +1,38 @@
+## Show that the archive library emits error messages when adding malformed
+## objects.
+
+# RUN: rm -rf %t.dir
+# RUN: split-file %s %t.dir
+# RUN: cd %t.dir
+
+## Malformed bitcode object.
+# RUN: llvm-as input.ll -o input.bc
+# RUN: %python -c "with open('input.bc', 'a') as f: f.truncate(10)"
+# RUN: not llvm-ar rc bad.a input.bc 2>&1 | FileCheck %s --check-prefix=ERR1
+
+# ERR1: error: bad.a: Invalid bitcode signature
+
+## Non-bitcode malformed file.
+# RUN: yaml2obj input.yaml -o input.o
+# RUN: not llvm-ar rc bad.a input.o 2>&1 | FileCheck %s --check-prefix=ERR2
+
+# ERR2: error: bad.a: section header table goes past the end of the file: e_shoff = 0x9999
+
+## Don't emit an error if the symbol table is not required.
+# RUN: llvm-ar rcS good.a input.o input.bc
+# RUN: llvm-ar t good.a | FileCheck %s --check-prefix=CONTENTS
+
+# CONTENTS:      input.o
+# CONTENTS-NEXT: input.bc
+
+#--- input.ll
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-linux"
+
+#--- input.yaml
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  EShOff:  0x9999

test/Object/archive-unknown-filetype.test

@@ -0,0 +1,11 @@
+## Show that the archive library does not emit an error or add any symbols to
+## the archive symbol table, when it encounters an unknown file type, but still
+## adds the file to the archive.
+
+# RUN: echo something > %t
+# RUN: rm -f %t.a
+# RUN: llvm-ar rc %t.a %t
+# RUN: llvm-ar t %t.a | FileCheck %s --check-prefix=CONTENTS -DFILE=%basename_t
+# RUN: llvm-nm --print-armap %t.a | FileCheck %s --allow-empty --implicit-check-not={{.}}
+
+# CONTENTS: [[FILE]]